The CPVT-associated RyR2 Mutation G230C Enhances Store Overload-Induced Ca2{+} Release and Destabilizes the NH2-terminal domains

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited, life-threatening arrhythmogenic disorder. CPVT is caused by delayed afterdepolarizations (DADs) that are induced by spontaneous Ca2+ release during sarcoplasmic reticulum (SR) Ca2+ overload, a process also known as store overload induced Ca2+ release (SOICR). A number of mutations in the cardiac ryanodine receptor (RyR2) are linked to CPVT. Many of these CPVT-associated RyR2 mutations enhance the propensity for SOICR and DADs by sensitizing RyR2 to luminal or luminal/cytosolic Ca2+ activation. Recently, a novel CPVT RyR2 mutation, G230C, was found to increase the cytosolic, but not the luminal, Ca2+ sensitivity of single RyR2 channels in lipid bilayers. This observation leads to the suggestion of a SOICR-independent disease mechanism for the G230C mutation. However, the cellular impact of this mutation on SOICR has yet to be determined. To this end, we generated stable, inducible HEK293 cell lines expressing the RyR2 WT and the G230C mutant. Using single cell Ca2+ imaging, we found that the G230C mutation markedly enhanced the propensity for SOICR and reduced the SOICR threshold. Furthermore, the G230C mutation increased the sensitivity of single RyR2 channels to both luminal and cytosolic Ca2+ activation and the Ca2+ dependent activation of [3H]ryanodine binding. In addition, the G230C mutation decreased the thermal stability of the N-terminal...
Source: BJ Cell - Category: Biochemistry Authors: Tags: BJ Disease Source Type: research